1 //===-- MipsELFObjectWriter.cpp - Mips ELF Writer -------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "MCTargetDesc/MipsBaseInfo.h" 11 #include "MCTargetDesc/MipsFixupKinds.h" 12 #include "MCTargetDesc/MipsMCTargetDesc.h" 13 #include "llvm/MC/MCAssembler.h" 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCSection.h" 17 #include "llvm/MC/MCValue.h" 18 #include "llvm/Support/ErrorHandling.h" 19 #include <list> 20 21 using namespace llvm; 22 23 namespace { 24 struct RelEntry { 25 RelEntry(const ELFRelocationEntry &R, const MCSymbol *S, int64_t O) : 26 Reloc(R), Sym(S), Offset(O) {} 27 ELFRelocationEntry Reloc; 28 const MCSymbol *Sym; 29 int64_t Offset; 30 }; 31 32 typedef std::list<RelEntry> RelLs; 33 typedef RelLs::iterator RelLsIter; 34 35 class MipsELFObjectWriter : public MCELFObjectTargetWriter { 36 public: 37 MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI, 38 bool _isN64, bool IsLittleEndian); 39 40 virtual ~MipsELFObjectWriter(); 41 42 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 43 bool IsPCRel) const override; 44 virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 45 const MCValue &Target, 46 const MCFragment &F, 47 const MCFixup &Fixup, 48 bool IsPCRel) const; 49 virtual void sortRelocs(const MCAssembler &Asm, 50 std::vector<ELFRelocationEntry> &Relocs); 51 }; 52 } 53 54 MipsELFObjectWriter::MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI, 55 bool _isN64, bool IsLittleEndian) 56 : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS, 57 /*HasRelocationAddend*/ (_isN64) ? true : false, 58 /*IsN64*/ _isN64) {} 59 60 MipsELFObjectWriter::~MipsELFObjectWriter() {} 61 62 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 63 const MCValue &Target, 64 const MCFragment &F, 65 const MCFixup &Fixup, 66 bool IsPCRel) const { 67 assert(Target.getSymA() && "SymA cannot be 0."); 68 const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol(); 69 70 if (Sym.getSection().getKind().isMergeableCString() || 71 Sym.getSection().getKind().isMergeableConst()) 72 return &Sym; 73 74 return NULL; 75 } 76 77 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target, 78 const MCFixup &Fixup, 79 bool IsPCRel) const { 80 // determine the type of the relocation 81 unsigned Type = (unsigned)ELF::R_MIPS_NONE; 82 unsigned Kind = (unsigned)Fixup.getKind(); 83 84 switch (Kind) { 85 default: 86 llvm_unreachable("invalid fixup kind!"); 87 case FK_Data_4: 88 Type = ELF::R_MIPS_32; 89 break; 90 case FK_Data_8: 91 Type = ELF::R_MIPS_64; 92 break; 93 case FK_GPRel_4: 94 if (isN64()) { 95 Type = setRType((unsigned)ELF::R_MIPS_GPREL32, Type); 96 Type = setRType2((unsigned)ELF::R_MIPS_64, Type); 97 Type = setRType3((unsigned)ELF::R_MIPS_NONE, Type); 98 } 99 else 100 Type = ELF::R_MIPS_GPREL32; 101 break; 102 case Mips::fixup_Mips_GPREL16: 103 Type = ELF::R_MIPS_GPREL16; 104 break; 105 case Mips::fixup_Mips_26: 106 Type = ELF::R_MIPS_26; 107 break; 108 case Mips::fixup_Mips_CALL16: 109 Type = ELF::R_MIPS_CALL16; 110 break; 111 case Mips::fixup_Mips_GOT_Global: 112 case Mips::fixup_Mips_GOT_Local: 113 Type = ELF::R_MIPS_GOT16; 114 break; 115 case Mips::fixup_Mips_HI16: 116 Type = ELF::R_MIPS_HI16; 117 break; 118 case Mips::fixup_Mips_LO16: 119 Type = ELF::R_MIPS_LO16; 120 break; 121 case Mips::fixup_Mips_TLSGD: 122 Type = ELF::R_MIPS_TLS_GD; 123 break; 124 case Mips::fixup_Mips_GOTTPREL: 125 Type = ELF::R_MIPS_TLS_GOTTPREL; 126 break; 127 case Mips::fixup_Mips_TPREL_HI: 128 Type = ELF::R_MIPS_TLS_TPREL_HI16; 129 break; 130 case Mips::fixup_Mips_TPREL_LO: 131 Type = ELF::R_MIPS_TLS_TPREL_LO16; 132 break; 133 case Mips::fixup_Mips_TLSLDM: 134 Type = ELF::R_MIPS_TLS_LDM; 135 break; 136 case Mips::fixup_Mips_DTPREL_HI: 137 Type = ELF::R_MIPS_TLS_DTPREL_HI16; 138 break; 139 case Mips::fixup_Mips_DTPREL_LO: 140 Type = ELF::R_MIPS_TLS_DTPREL_LO16; 141 break; 142 case Mips::fixup_Mips_Branch_PCRel: 143 case Mips::fixup_Mips_PC16: 144 Type = ELF::R_MIPS_PC16; 145 break; 146 case Mips::fixup_Mips_GOT_PAGE: 147 Type = ELF::R_MIPS_GOT_PAGE; 148 break; 149 case Mips::fixup_Mips_GOT_OFST: 150 Type = ELF::R_MIPS_GOT_OFST; 151 break; 152 case Mips::fixup_Mips_GOT_DISP: 153 Type = ELF::R_MIPS_GOT_DISP; 154 break; 155 case Mips::fixup_Mips_GPOFF_HI: 156 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 157 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 158 Type = setRType3((unsigned)ELF::R_MIPS_HI16, Type); 159 break; 160 case Mips::fixup_Mips_GPOFF_LO: 161 Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type); 162 Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type); 163 Type = setRType3((unsigned)ELF::R_MIPS_LO16, Type); 164 break; 165 case Mips::fixup_Mips_HIGHER: 166 Type = ELF::R_MIPS_HIGHER; 167 break; 168 case Mips::fixup_Mips_HIGHEST: 169 Type = ELF::R_MIPS_HIGHEST; 170 break; 171 case Mips::fixup_Mips_GOT_HI16: 172 Type = ELF::R_MIPS_GOT_HI16; 173 break; 174 case Mips::fixup_Mips_GOT_LO16: 175 Type = ELF::R_MIPS_GOT_LO16; 176 break; 177 case Mips::fixup_Mips_CALL_HI16: 178 Type = ELF::R_MIPS_CALL_HI16; 179 break; 180 case Mips::fixup_Mips_CALL_LO16: 181 Type = ELF::R_MIPS_CALL_LO16; 182 break; 183 case Mips::fixup_MICROMIPS_26_S1: 184 Type = ELF::R_MICROMIPS_26_S1; 185 break; 186 case Mips::fixup_MICROMIPS_HI16: 187 Type = ELF::R_MICROMIPS_HI16; 188 break; 189 case Mips::fixup_MICROMIPS_LO16: 190 Type = ELF::R_MICROMIPS_LO16; 191 break; 192 case Mips::fixup_MICROMIPS_GOT16: 193 Type = ELF::R_MICROMIPS_GOT16; 194 break; 195 case Mips::fixup_MICROMIPS_PC16_S1: 196 Type = ELF::R_MICROMIPS_PC16_S1; 197 break; 198 case Mips::fixup_MICROMIPS_CALL16: 199 Type = ELF::R_MICROMIPS_CALL16; 200 break; 201 case Mips::fixup_MICROMIPS_GOT_DISP: 202 Type = ELF::R_MICROMIPS_GOT_DISP; 203 break; 204 case Mips::fixup_MICROMIPS_GOT_PAGE: 205 Type = ELF::R_MICROMIPS_GOT_PAGE; 206 break; 207 case Mips::fixup_MICROMIPS_GOT_OFST: 208 Type = ELF::R_MICROMIPS_GOT_OFST; 209 break; 210 case Mips::fixup_MICROMIPS_TLS_GD: 211 Type = ELF::R_MICROMIPS_TLS_GD; 212 break; 213 case Mips::fixup_MICROMIPS_TLS_LDM: 214 Type = ELF::R_MICROMIPS_TLS_LDM; 215 break; 216 case Mips::fixup_MICROMIPS_TLS_DTPREL_HI16: 217 Type = ELF::R_MICROMIPS_TLS_DTPREL_HI16; 218 break; 219 case Mips::fixup_MICROMIPS_TLS_DTPREL_LO16: 220 Type = ELF::R_MICROMIPS_TLS_DTPREL_LO16; 221 break; 222 case Mips::fixup_MICROMIPS_TLS_TPREL_HI16: 223 Type = ELF::R_MICROMIPS_TLS_TPREL_HI16; 224 break; 225 case Mips::fixup_MICROMIPS_TLS_TPREL_LO16: 226 Type = ELF::R_MICROMIPS_TLS_TPREL_LO16; 227 break; 228 } 229 return Type; 230 } 231 232 // Return true if R is either a GOT16 against a local symbol or HI16. 233 static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) { 234 if (!R.Sym) 235 return false; 236 237 MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol()); 238 239 return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) || 240 (R.Reloc.Type == ELF::R_MIPS_HI16); 241 } 242 243 static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) { 244 if (I == Last) 245 return false; 246 247 RelLsIter Hi = I++; 248 249 return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) && 250 (Hi->Offset == I->Offset); 251 } 252 253 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) { 254 return R0.Sym == R1.Sym; 255 } 256 257 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) { 258 return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1); 259 } 260 261 void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm, 262 std::vector<ELFRelocationEntry> &Relocs) { 263 // Call the default function first. Relocations are sorted in descending 264 // order of r_offset. 265 MCELFObjectTargetWriter::sortRelocs(Asm, Relocs); 266 267 RelLs RelocLs; 268 std::vector<RelLsIter> Unmatched; 269 270 // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs 271 // are in ascending order of r_offset. 272 for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin(); 273 R != Relocs.rend(); ++R) { 274 std::pair<const MCSymbolRefExpr*, int64_t> P = 275 MipsGetSymAndOffset(*R->Fixup); 276 RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0, 277 P.second)); 278 } 279 280 // Get list of unmatched HI16 and GOT16. 281 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 282 if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end())) 283 Unmatched.push_back(R); 284 285 // Insert unmatched HI16 and GOT16 immediately before their matching LO16. 286 for (std::vector<RelLsIter>::iterator U = Unmatched.begin(); 287 U != Unmatched.end(); ++U) { 288 RelLsIter LoPos = RelocLs.end(), HiPos = *U; 289 bool MatchedLo = false; 290 291 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) { 292 if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) && 293 (CompareOffset(*R, *HiPos) >= 0) && 294 ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) || 295 (!MatchedLo && !CompareOffset(*R, *LoPos)))) 296 LoPos = R; 297 298 MatchedLo = NeedsMatchingLo(Asm, *R) && 299 HasMatchingLo(Asm, R, --RelocLs.end()); 300 } 301 302 // If a matching LoPos was found, move HiPos and insert it before LoPos. 303 // Make the offsets of HiPos and LoPos match. 304 if (LoPos != RelocLs.end()) { 305 HiPos->Offset = LoPos->Offset; 306 RelocLs.insert(LoPos, *HiPos); 307 RelocLs.erase(HiPos); 308 } 309 } 310 311 // Put the sorted list back in reverse order. 312 assert(Relocs.size() == RelocLs.size()); 313 unsigned I = RelocLs.size(); 314 315 for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) 316 Relocs[--I] = R->Reloc; 317 } 318 319 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, 320 uint8_t OSABI, 321 bool IsLittleEndian, 322 bool Is64Bit) { 323 MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI, 324 (Is64Bit) ? true : false, 325 IsLittleEndian); 326 return createELFObjectWriter(MOTW, OS, IsLittleEndian); 327 } 328